דע מה למעלה ממך עין רואה
Know what is above you: a seeing eye… 
Elsewhere in the Talmud, we’re told to remember “before Whom” we stand, when we pray. In this passage in Pirkei Avot, Rabbi Yehudah ha-Nasi, known affectionately as “Rabbi,” tells us to contemplate [הסתכל] three things deeply, to avoid doing wrong, mistaken actions: All that we do is “seen,” “heard” and “remembered.” The remembrance of these, if sufficiently impressed upon ourselves, will help us exercise self-control over urges and impulses which could otherwise be expressed unchecked.
It’s well-established in law enforcement that “surveillance equals deterrence.”
Rabbi urges us to consider deeply that everything we do is being “seen” and “remembered” — “written in a book,” as it were — as a tool to deter ourselves from doing what we might know to be wrong, but what might also seem most immediately expedient or pleasurable.
This is called the “fear of ‘G-d’ or ‘Heaven’.” It has become the single most unpopular phrase in the Bible for many people, because of its being misunder-stood as a disproportionate, unexpected punishment from an “angry G-d” — an “ayin ha-ra” [עין הרע], an “evil eye,” as it were.
Instead, it means an “ayin ro’eh” [עין רואה] — a “seeing eye” — an inevitable, inescapable Divine awareness of all our actions and thoughts by a G-d Whose response is infinitely Fair. We have much more to fear from ourselves than we do from G-d.
I previously wrote about G-d’s response as proportionate to our acts and the circumstances under which they’re done: https://rabbielimallon.wordpress.com/2011/02/02/2-2-11-torah-and-karma/
Perhaps that’s why the “fear of G-d” is called “the beginning of wisdom” in both “Psalms”  and “Proverbs.”  What is “wisdom”? Realistically foresee-ing the consequences of our own actions.
The “fear of G-d” has two major levels, of which “fear of punishment” (“yirat ha-onesh”) is the preliminary, lower, albeit necessary one.
The “higher fear” is “awe of Divine Majesty” (“yirat ha-romemut”). 
In English, “fear” can imply a range of emotions that stretches from mild appre-hension or trepidation to abject terror; even phobia. King David, King Solomon and Rabbi hardly intended to say: “Have a phobic fear of punishment, regard-less of what you do.” They meant: G-d isn’t just in Temple or synagogue (or church or masjid or mandir, for that matter); G-d ‘sees‘ you, wherever you are. Consequences are inevitable.”
Knowing that we often have great difficulty controlling ourselves, Rabbi gives us a wonderful, simple technique for doing so — for our own good: “Remember that you’re ‘seen‘.” Develop it as a habitual way of thinking, until it becomes “second nature” to you. Properly understood, he’s showing us great compas-sion.
Certainly, we live in a world in which it’s easy to say that others lack “the fear of G-d”: The business person so intent on profit that the well-being of the community — of the world — ceases to matter at all; the terrorist or zealot — or soldier — who’s willing to kill unarmed, defenseless people to promote the views he/she supports; the politician offering empty lies and false promises in place of genuine leadership; and so on.
“The fear of G-d is the beginning of wisdom.” So — “Remember what’s above you…”
Rabbi doesn’t ask us to judge others. He reminds us: What we do ourselves, we also do to ourselves.
We might say, then: A highly practical and realistic concern with ultimately having to “pay” for our wrongs would be at least “the beginning of wisdom” on our part.
It’s also the necessary beginning of a path of spiritual progress that leads through the inner peace of “awe” of G-d, ultimately to the bliss of loving G-d Who is always, only Good.